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- Englisch (2)
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- Bone (1)
- D-nozzle (1)
- NMR (1)
- Phased array technique (1)
- Protein-mineral-interface (1)
- Real and simulated cracks (1)
- SAFT reconstruction (1)
- Stress corrosion cracking (1)
Hydrogen-bearing species in the bone mineral environment were investigated using solid-state NMR spectroscopy of powdered bone, deproteinated bone, and B-type carbonated apatite. Using magic-angle spinning and cross-polarization techniques three types of structurally-bound water were observed in these materials. Two of these water types occupy vacancies within the apatitic mineral crystal in synthetic carbonated apatite and deproteinated bone and serve to stabilize these defect-containing crystals. The third water was observed at the mineral surface in unmodified bone but not in deproteinated bone, suggesting a role for this water in mediating mineral-organic matrix interactions. Direct evidence of monohydrogen phosphate in a 1H NMR spectrum of unmodified bone is presented for the first time. We obtained clear evidence for the presence of hydroxide ion in deproteinated bone by 1H MAS NMR. A 1H-31P heteronuclear correlation experiment provided unambiguous evidence for hydroxide ion in unmodified bone as well. Hydroxide ion in both unmodified and deproteinated bone mineral was found to participate in hydrogen bonding with neighboring water molecules and ions. In unmodified bone mineral hydroxide ion was found, through a 1H-31P heteronuclear correlation experiment, to be confined to a small portion of the mineral crystal, probably the internal portion.
Stress corrosion cracking is a transcrystalline or intercrystalline crack formation in materials which
occurs under the influence of static tensile stress or residual stress and a specific aggressive
medium such as chloride containing substances.
This special sort of crack formation is involved in complex crack configurations, which may
only insufficiently be captured by conventional ultrasonic probes with fixed angles of incidence.
Only a number of different beam angles produce sufficient reflection to reconstruct the complete
defect shape from measured ultrasonic data. The SAFT algorithm, which was recently successfully
used in many industrial NDT-applications, is a promising tool for the reconstruction process. In
addition, the combination of phased array technique and SAFT was developed in several projects
by BAM, Berlin. Investigations using phased array equipment were performed to look into crack
configurations in test blocks with different surface curvatures. UT-SAFT has been used for the
analysis of spark-eroded notches simulating stress corrosion cracks at the thermo sleeve weld of a
nozzle. For comparison, UT-SAFT has also been applied for the analysis of real reflectors at the
same position in a nozzle used in a power plant, which was repaired later on. SAFT-scans received
from reconstructed ultrasonic measurement data confirm the practical usefulness of the SAFTalgorithm
developed by BAM.